Re: Was: iostat output; Now: Disk storage technologies

I'm not cringing at all - quite the contrary.  DBAs are hampered today 
by the fact that their applications, moreso than most others, are 
closely tied to the storage the servers are attached to.  At the same 
time, though, storage technology has become complex enough that its 
practicaly a whole separate skill set.    So, Oracle DBAs ideally have 
to be experts at both - a tall task, to say the least.

Storage vendors haven't helped this either - they've found a lucrative 
market in professional services for their storage products and are 
invested in the "CIO sell".  When I was at EMC, I took their sales 
training, and the conventional wisdom was that it was a waste of time 
to sell to DBAs and other "pure tech" customers- to ignore them and go 
right over their heads to their management.

DBAs are thus kind of left out in the cold - ignored by the vendors, 
pushed towards consultant implementations, poor documentation, and a 
constantly developing set of technologies.  It's a rough road.

To go on to the pure tech topics, I think the biggest correction I 
would make is that SAN == high end.  This certainly was true 5-7 years 
ago, but today, SAN is available to every organization.  EMC, HP, and 
Dell are all working on shipping a SAN bundle for sub-$10k prices.  The 
end result of this is that DAS is going to be pushed out of existence - 
its only a matter of time.  Now, its true, the low-end SAN products 
don't ship with the featureset of the large monolithic arrays (HP 
XP-series, EMC Symmetrix, HDS 9980), but they are effectively 
supplanting DAS in new installs.

The performance and featureset of NAS is a common misconception as 
well.  I'm definitely a NAS cheerleader, within reason, but NAS has 
rapidly moved out of the realm of office fileservers and development 
environments into serious large-scale and high-performance 
environments.  BlueArc, for example, ships a NAS array capable of over 
a 1GB/sec. of I/O, and they're going to be up to 2GB/sec. by the end of 
the year.  In addition, the higher-end NAS boxes from companies such as 
Network Appliance and BlueArc support all of the features you tied to 
SAN - dial-home, dynamic cache partitioning, snapshots, remote 
replication, etc.

It gets even MORE complicated when you look at the multi-protocol 
support available on some of the arrays.  NetApp filers support NAS, 
Fibre Channel, and iSCSI all from the same box (and exposing the same 
storage through multiple protocols!) - EMC Symmetrix does both iSCSI 
and FC from one array.

Which dovetails nicely into iSCSI - iSCSI will replace Fibre Channel at 
some point.  Fibre Channel is just too expensive (still around 
$1000/port!) and complex to last in the face of iSCSI, which can run 
over existing networks, leverage already-developed skillsets and 
provide identical performance.  The only limiting factor for iSCSI 
today is the relative newness of the implementations and the lack of 
good hardware offload cards.  The reason fibre channel is so fast is 
because most of the protocol is handled in dedicated processors on the 
card, leaving the host free to do other things.  Software iSCSI over 
normal gigabit cards has to do all of the I/O on the host CPUs, 
significantly decreasing the throughput.  At the moment, iSCSI is 
neither a low-end or high-end solution - its more of a solution for 
early adopters looking for block-based I/O at a lower price point.

Hopefully this is informative - thanks for the chance to pontificate...

Matt

--
Matthew Zito
GridApp Systems
Email: mzito@xxxxxxxxxxx
Cell: 646-220-3551
Phone: 212-358-8211 x 359
http://www.gridapp.com


On Apr 29, 2004, at 1:05 PM, John Kanagaraj wrote:

> Matt,
>
>> You can respond to me directly if you like - unless the list at large
>> is interested in iSCSI on netapp.
>
> I would very much like to keep this in the list..... The ground 
> beneath us
> as far as storage is concerned is moving quite quickly, and most of us 
> DBAs
> are still in the dark as far as Storage concepts and directions go. 
> Many are
> not aware that there is a wide variety of solutions as far as disk 
> storage
> is concerned, and the DBA world is just now getting a handle on the
> transition from DAS (Direct Attached Storage) to SAN (Storage Area 
> Networks)
> or NAS (Network Attached Storage). And in comes comes iSCSI (or a
> combination of the above) to cloud the picture.... As far as I 
> understand
> the technology, we have:
> -----------------------------------------------------------------

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